1. Field of the Invention
This invention concerns an automotive vehicle which is economically assembled from a plastic body and a metal frame, and more particularly concerns the manner of attachment of a modular plastic body to a metal frame.
2. Description of the Prior Art
The body and chassis of motor vehicles such as automobiles, vans, and trucks are constructed in either of two ways. One way is to assemble, mostly through welding, various pre-formed sheet steel panels to create the body of the vehicle, then to bolt the body to a supporting metal framework known as the chassis. Another way is to construct the body and the chassis together as a monocoque, i.e., all parts of the body and the chassis are welded together as a single unit. Although both methods produce high quality vehicles, these methods have several disadvantages.
Firstly, these manufacturing processes are complex and expensive. They require a vast number of steps including the stamping of each separate body and chassis part and the assembling and welding of each of these parts to the others to create a complete body and chassis. This generally requires large investments in factory equipment and the requisite dies, so much so that stamping runs of less than tens of thousands are generally unprofitable. It also makes it difficult to use this method to manufacture vehicles that would be sufficiently inexpensive to be affordable to less affluent individuals in the less developed countries of the world.
Secondly, steel body panels tend to deform and dent when struck with anything but the lightest of forces. These vehicles are therefore easily damaged, resulting in high insurance and repair costs.
Plastic body panels are dent and rust resistant but lack the structural strength of steel panels. By way of reinforcement with fiberglass or other high modulus fibers, plastic panels achieve considerably greater strength. Another technique for increasing the strength and stiffness of plastic automotive panels is to incorporate a reinforcing foam structure into the interior surface or core layer of the panel.
The attachment of plastic components to a vehicle chassis fabricated of steel or other strong metals is complicated by the fact that load-bearing, torsional bending stresses, and vibrational effects cause deterioration of the metal/plastic interface.
U.S. Pat. No. 6,457,768 discloses plastic vehicle body panels containing structural fiber material molded into the panels.
U.S. Pat. No. 4,917,435 discloses a truck cab fabricated by interengagement of a unitary upper plastic member with a unitary lower plastic member having floor and rear wall portions. Said interengagement is secured by adhesive bonding applied at interlocking edges. Similarly, U.S. Pat. No. 4,759,489 describes the production of an automobile body by joining an upper module with a lower module having a floor portion.
U.S. Pat. No. 5,195,779 discloses plastic vehicle side panels comprised of a foam core sandwiched between outer skin layers, and attachment of said side panels to a body structure by way of specialized interactive fittings.
U.S. Pat. No. 5,660,427 describes the production of a passenger cab shell from a plurality of plastic panels assembled together along overlapping edge portions. The cab shell is then attached to a plastic truck box portion.
U.S. Pat. No. 5,314,230 discloses the joinder of two halves of a plastic upper body member which in turn are joined to a fiber reinforced lower member to comprise a monocoque vehicle assembly. Said joinder is achieved by interactive channel and guide structures which receive adhesive.
U.S. Pat. No. 5,228,742 describes apparatus for connecting a composite outer body of a vehicle to a composite underbody, said apparatus comprising interconnecting flexible tabs which permit relative movement of said outer body with respect to said underbody.
U.S. Pat. No. 5,915,781 discloses the joinder of plastic vehicle body members by injecting an adhesive into a channel cavity formed at the interface of the body members.
U.S. Pat. No. 5,129,700 describes a vehicle frame that supports a floor pan defining the bottom of the interior of a vehicle. The floor pan is provided with attachment devices for fixing the floor pan to the frame, said attachment devices including bolts and elastic adhesive.
U.S. Pat. No. 5,806,620 discloses an automobile having a plastic body bonded to a steel frame and a unitary plastic front end pivotably connected to the frame and releasably connectable to the body by means of elastic straps.
U.S. Pat. No. 5,964,490 describes a plastic automobile body bonded to a steel frame by an adhesive layer deposited between the body and frame to accommodate thermal expansion effects.
U.S. Pat. No. 5,879,042 discloses a rigid box-like coupler having two open ends for coupling car body parts.
U.S. Pat. No. 4,453,763 discloses an automobile having a plastic tub supported by a steel frame chassis. Outwardly directed flanges at the tub's outer edge rest directly on the frame except in limited areas where the tub is secured to the frame with bolted plates and intervening bushings. Although such manner of securement may lessen the effects of vertical stress forces, it is ineffective in coping with horizontally directed forces.
British Patent 0910251 discloses a motor car having a unitary laminated fiberglass body and chassis with embedded metal bracing.
U.S. Pat. No. 3,632,156 discloses a unitary plastic body with inverted channels that engage side bars in the underlying chassis.
French Patent 1.247.668 teaches the use of a vibration absorbing elastic bushing interposed between a downwardly open trough of the body of a vehicle and a semi-spherical part of the frame.
U.S. Pat. No. 1,707,214 discloses a joint between the body and chassis of an automobile having a bushing bonded to bolted plates.
U.S. Pat. No. 4,352,520 teaches the use of a bushing member with a Shore A hardness of 45 as an insert between the body and chassis of a vehicle.
U.S. Pat. No. 3,415,568 describes a vehicle body underframe comprising a unitary body and chassis with outer and inner shell members defining therebetween a cavity which is filled with a hard plastic foam.
Although the aforesaid Patents address the issue of joining plastic body components to chassis or frame components of a vehicle, they do not resolve the challenge of providing a durable low cost vehicle having plastic body components.
Durability can only be achieved if the plastic components, which lack the strength, toughness and hardness of metals, are adequately protected from early structural failure. Such protection involves the following factors: Firstly, the plastic body must be protected from the twisting, bending and load-carrying stresses borne by the vehicle. This is best done by causing the chassis to be strong and rigid enough to withstand such stresses without deformation and providing extensive areas which resiliently support the body.
Secondly, the modular plastic body must, itself, be internally reinforced so that it will resist damage by loads and other forces to which it may be subjected.
Thirdly, the plastic body must be equipped with extensive downwardly directed means interactive with the chassis to prevent downward, upward, sideward, forward and rearward displacement of the body on the chassis and to disperse all forces transmitted from the chassis to the plastic body over a wide area of interaction.
Fourthly, extensive protective bushings must be interposed in all the areas of supportive attachment between the plastic body and the chassis to prevent fragmentation and abrasive erosion of the relatively soft and brittle plastic material at said metal/plastic interface. In combination, the aforesaid factors have been found capable of providing a durable low cost vehicle having a modular plastic body.
It is accordingly an object of the present invention to provide an inexpensive motor vehicle having a modular plastic body joined to a conventional metal chassis.
It is a further object of this invention to provide a plastic vehicle body adapted to be mounted onto a steel chassis in a manner to distribute the stresses of load-bearing and vibration over broad areas of the plastic body.
It is an additional object of the present invention to provide a steel chassis adapted to provide support to a modular plastic body in a manner to distribute the stresses of load-bearing and vibration over substantially broad areas of the plastic body sufficiently to prevent any particular point of said plastic body from being subjected to destructive concentrated torsional, flexural or load-bearing forces.
It is still an additional object of this invention to provide a plastic vehicle body mounted on a steel chassis in a manner to interlock said chassis and said plastic body over broad areas of inter-engagement as to restrict downward, upward, forward, rearward and sideward movement of said body relative said chassis.
It is another object of this invention to provide shock absorbing means for attaching a modular plastic vehicle body to a steel chassis over substantially all areas of attachment.
It is still another object of this invention to provide an inexpensive motor vehicle having a modular plastic body joined to a metal chassis wherein said plastic body is strengthened by reinforcement material.
These objects and other objects and advantages of the invention will be apparent from the following description.